Most answers found by google mention that your ODS (on disk structure) is too new for your Firebird version.
But in this case, the portname was pointing to InterBase 2009 (relatively new) in stead of Firebird (2.1.1) also relatively new.

Firebird 2.1.1 was running on port fbs_211 (decimal 30521), but the jdbc Firebird driver does not understand service names like fbs_211, only hard-coded TCP/IP ports like 30521.
InterBase 2009 was running onport 3050.